In the area of energy production, oil-containing fuels such as crude and heavy oils, which are available as inexpensive fuels for energy production by gas turbines, are frequently relied on. However, such crude and heavy oils contain asphaltenes, which in turn contain chemically-bound heavy metals. In combustion of these oils, heavy metals such as vanadium or nickel are released as metal oxides. The metal oxides form alloys with the metals of the turbine blades and corrode or weaken them.
In addition, regardless of their metal content, asphaltenes have the property of being precipitated as a solid on sudden changes in pressure or temperature. These solid asphaltene particles can block lines or fine nozzles of the burner used and thus have a sustained effect on mixture formation in the turbine, reducing its efficiency.
Accordingly, an inhibitor is added to oils containing vanadium that prevents alloying of the metal oxides with the metal of the turbine blades. In the case of a magnesium additive that is commonly used as an inhibitor but is costly, a high-melting magnesium forms rather than low-melting alkali vanadates. In this case, however, there is a risk of crust formation on the turbine blades through layered precipitation of the magnesium vanadate. In order to ensure the functioning of the turbine and preserve aerodynamic quality/efficiency, the precipitates or crusts must be removed from the turbine blades, which requires regular time- and cost-intensive servicing. More particularly, such cleaning requires that the turbine be shut down for several hours.
For more sensitive turbines, for example those with gas-cooled blades, the problem of blockage of the burner nozzles by undesirable asphaltene precipitates or blockage of the cooling channel by vanadates has not yet been solved.
Moreover, so-called deasphalting processes are known that are based on extraction of asphaltenes with aliphatic hydrocarbons as precipitants. However, these processes for asphaltene reduction are used only in the area of refineries. Use in the area of power plants is not appropriate, because, for example, “classical” deasphalting by means of the so-called ROSE process involves asphaltene extraction with low-molecular aliphatics that require residence times of up to several hours. In the ROSE process in particular, such deasphalting involves high temperatures and pressure in the “critical” range of the solvents.
With respect to the typical requirements of power plants of oil inflow of 200 t/h and low operating costs, classical processes must also be dimensioned differently than in a refinery. On the one hand, low residence times are required to increase throughput, and on the other, in the case of typically observed single-cycle gas turbine power plants, there is enough “cost-free” waste heat available to allow operation of the process without external heating and the addition fuel costs associated therewith.